Politicians do what they must to get re-elected. So it’s not unexpected that Republican senators like Richard Lugar and Orrin Hatch would swing sharply to the right to fend off primary challengers.

As Jonathan Weisman reported in The Times on Sunday, Hatch has a lifetime rating of 78 percent from the ultra-free market Club for Growth, but, in the past two years, he has miraculously jumped to 100 percent and 99 percent, respectively. Lugar has earned widespread respect for his thoughtful manner and independent ways.

Now he’s more of a reliable Republican foot soldier.

Still, it is worth pointing out that this behavior is not entirely honorable. It’s not honorable to adjust your true nature in order to win re-election. It’s not honorable to kowtow to the extremes so you can preserve your political career.

But, of course, this is exactly what has been happening in the Republican Party for the past half century. Over these decades, one pattern has been constant: Wingers fight to take over the party, mainstream Republicans bob and weave to keep their seats.

In the 1960s and ‘70s, the fight was between conservatives and moderates. Conservatives trounced the moderates and have driven them from the party. These days the fight is between the protesters and the professionals. The grass-roots protesters in the Tea Party and elsewhere have certain policy ideas, but they are not that different from the Republicans in the “establishment.”

The big difference is that the protesters don’t believe in governance. They have zero tolerance for the compromises needed to get legislation passed. They don’t believe in trimming and coalition building.

For them, politics is more about earning respect and making a statement than it is about enacting legislation.

It’s grievance politics, identity politics.

Of course, the professional politicians don’t want to get in the way of this torrent of passion and resentment. In private, they bemoan where the party is headed; in public they do nothing.

But where have these party leaders been over the past five years, when all the forces that distort the GOP were metastasizing? Where were they during the rise of Sarah Palin and Glenn Beck? Where were they when Arizona passed its beyond-the-fringe immigration law? Where were they in summer 2011 when the House Republicans rejected even the possibility of budget compromise? They were lying low, hoping the unpleasantness would pass.

The wingers call their Republican opponents RINOs, or Republican In Name Only. But that’s an insult to the rhino, which is a tough, noble beast. If RINOs were like rhinos, they’d stand up to those who seek to destroy them.

Actually, what the country needs is some real Rhino Republicans. But the professional Republicans never do that. They’re not rhinos. They’re Opossum Republicans. They tremble for a few seconds then slip into an involuntary coma every time they’re challenged aggressively from the right.

Without real opposition, the wingers go from strength to strength. Under their influence, we’ve had a primary campaign that isn’t really an argument about issues. It’s a series of heresy trials in which each of the candidates accuse the others of tribal impurity. Two kinds of candidates emerge from this process: first, those who are forceful but outside the mainstream; second, those who started out mainstream but look weak and unprincipled because they have spent so much time genuflecting before those who despise them.

Neither is likely to win in the fall. Before the GOP meshugana campaign, independents were leaning toward the GOP. But, in the latest Politico/George Washington University Battleground Poll, Obama leads Mitt Romney among independents by 49 percent to 27 percent.

Leaders of a party are supposed to educate the party, to police against its worst indulgences, to guard against insular information loops.

They’re supposed to define a creed and establish boundaries. Republican leaders haven’t done that. Now the old pious cliche applies:

First they went after the Rockefeller Republicans, but I was not a Rockefeller Republican. Then they went after the compassionate conservatives, but I was not a compassionate conservative.

Then they went after the mainstream conservatives, and there was no one left to speak for me.